it is understood by soil salinization the excessive accumulation of mineral salts in the form of ions (Na+ and Cl-) on the surface and also on the interior structure of the relief used for planting. It is a process that most commonly manifests itself in areas with an arid and semi-arid climate where evaporation rates are high and the average amounts of rainfall very low.
We know that, naturally, water has mineral salts and other compounds, such as potassium and many others. However, the excessive accumulation of this water in the soil, added to its high rate of evaporation, can cause the salinization process, as the deposited salts do not evaporate together. Thus, when rainfall is low and the soil is poorly washed by the runoff of rainwater on the surface, these salts remain even more accumulated, causing you to lose your fertility and even intensifying processes of desertification.
There are three main causes for soil salinization: the rise in the water table, the adoption of incorrect irrigation methods and the accumulation of salt water from the seas and oceans.
In the case of the emergence of groundwater to the surface, there is a greater presence of this water in the soils of regions arid and semi-arid non-irrigated, with the accumulation of salts due to intense evaporation, given the climate dry. For this to happen, the subsoil water level must obviously be close to the surface, which is more common in regions floodplains and also in areas of relative and absolute depression, in addition to the presence of the aforementioned climatic types.
Incorrect irrigation methods cause or, in some cases, only intensify already existing soil salinization processes. Therefore, in environments that already show this trend - again, in regions with a drier and more intense climate evaporation -, sprinkler irrigation techniques or other managements that use a lot of water are little recommended. The correct thing, in theory, is the use of dripping techniques, in which the use of water is more contained, affecting the soil to a lesser degree. The big problem is that these techniques are more expensive, which contrasts with the economic level of producers in arid regions, usually (but not always) of low purchasing power, which practically makes it impossible to use techniques that seek to avoid the salinization.
Do not stop now... There's more after the advertising ;)
In a last type of occurrence, we mention the cases of soil salinization due to the presence – or rather, the absence! – of sea water. In regions like the Dead Sea it's the Aral Sea, in Asia, the climate is dry and the evaporation of salt water from these seas (which, in fact, are lakes) is very intense. Depending on the use and exploitation of these water resources, there may be a loss or lesser presence of water. Because of this, mineral salts remain on the surface, while the concentration of liquid decreases, which leads to the accumulation of these salts and the consequent and inevitable salinization.
Dry area of the Aral Sea in Kazakhstan. Soil salinity, in this case, is very high
As we have already mentioned, the main consequences of the soil salinization process are the loss of arable areas, the death of cultivated vegetables (mainly beans, onions, potatoes and other more sensitive types), in addition to increasing the possibility of desertification. There are containment measures, such as soil correction or even desalination by drainage, but the most correct thing is to prevent such occurrences, with correct irrigation techniques and the monitoring and control of the salinity indices of water and of the soils.
By Me. Rodolfo Alves Pena
